Transport device for transporting test strips in an analysis system

ABSTRACT

According to the invention the analytical system includes a transport unit which is driven by piezoactive elements. The transport unit enables a direct or indirect transport of the test elements thus enabling a complete or partial automation of analytical methods. Furthermore the invention encompasses a transport unit for transporting a test element which according to the invention is controlled by an optical detector which detects the test element in the system.

REFERENCE TO RELATED APPLICATIONS

The present application claims priority to PCT Application No.PCT/EP2003/014709 filed Dec. 22, 2003, German Patent Application No.10310935.8, filed Mar. 13, 2003; and European Patent Application02028894.0 filed Dec. 23, 2002.

TECHNICAL FIELD

The present invention is within the field of sample liquid analysis bytest elements.

BACKGROUND

Such test elements are often analyte-specific, disposable test elementswhich contain a reagent that can be used to determine an analyte. Insuch test elements the reagent of the test element interacts with ananalyte to be determined and thus induces a measurable, analyte-specificchange in the reagent. Optical systems which enable an analysis of thesample are often used to measure and evaluate the reagent fieldespecially in the case of an analyte-dependent change in the colour ofthe test element. The photometric evaluation of analytical test elementsis nowadays one of the most commonly used analytical methods for rapidlydetermining the concentration of analytes in samples. In generalphotometric evaluation is used in the field of analytics, environmentalanalytics and above all in medical diagnostics. Test elements that canbe evaluated photometrically or by reflection photometry are of majorimportance especially in the field of blood glucose determination incapillary blood. Such devices are for example used to monitor the bloodsugar level of diabetics such that their eating habits or insulininjections can be regulated on the basis of the blood glucose value ofthe drawn sample. Other examples of the use of optical systems are urinetest strips and test elements for other parameters such as lactate,creatinine, protein, uric acid and leucocytes. Furthermore reagent-freetest elements are also used in which an analyte to be determined canalso be measured with the aid of optical systems or for exampleelectrochemically.

In addition to the use of analytical instruments in hospitals by trainedmedical staff, such analytical systems have also been designed for thehome monitoring field to enable patients to monitor an analyte to bedetermined as regularly as possible. Common home monitoring analyticalsystems are used especially for blood glucose determinations. In thiscase the instrument is operated by the patient himself. In order toanalyse the blood, a test element on which an analytical field islocated is for example brought into contact with the blood of thepatient and subsequently inserted into the instrument by the user. Anoptical change which is dependent on the analyte concentration is forexample induced in the analytical field of the test element. The opticalchange in the light reflected or transmitted from the test element isdetected by a suitable optical measuring system to determine the bloodsugar concentration. Such a system is described for example in thedocument U.S. Pat. No. 5,424,035, which is hereby incorporated herein byreference. Furthermore such instruments are commercially available fromRoche Diagnostics GmbH, Mannheim Germany, under the names ACCUTREND®,ACCUCHEK®, GLUCOTREND®, and GLUCOMETER®. The structure of the testelements that are provided for use is shown for example in the documentU.S. Pat. No. 6,036,919, which is hereby incorporated by reference.

A general trend in carrying out analytical tests is to reduce the amountof sample required for the analysis. The reason for this is that oftenonly small amounts of sample are available. For example with blood sugardeterminations by diabetics a drop of blood is collected from the fingerpad. A reduction of the required quantity of blood can in this case helpto make the blood collection less painful for the person to be examined.The reason for this is that the puncture depth for blood collection canbe reduced when small sample volumes are required. The reduced samplequantity is associated with a miniaturization of the test element and inparticular of the detection zone in which for example the sample reactswith a reagent. However, in this connection it has turned out,especially with small amounts of sample, that changes in the technicalmeasuring conditions in analytical systems play a major role and causeconsiderable errors in the determination of the concentration of ananalyte. The reasons for technical changes in the measuring conditionsare for example a faulty positioning of the test element in theanalytical system so that for example it is not possible to evaluate thecomplete evaluation field of a test element. Hence an exact positioningof the test element in the analytical system is a prerequisite for anaccurate measurement. This has to be ensured in the home monitoringfield in which elderly and/or untrained persons often operate theinstrument. But, on the other hand, analytical systems with testelements are also used in commercial laboratories in which an automatedhandling of samples often has to be assured.

Consequently positioning elements are now being employed to accuratelyposition test elements in analytical systems. In this case the testelement has to be inserted and guided into the analytical system andremoved again either manually or automatically. In order to simplify thehandling for the user, more and more instruments are now provided withan automatic drive for the test element especially in the case ofinstruments that contain and have to handle a store of test elements.This results in the requirements for automatic drive units which, on theone hand, transport a test element to a site in the analytical systemand hold it in a defined position and, on the other hand, should enablethe handling of a plurality of test elements in a magazine. Moreover inaddition to the direct transport of the test element, it is oftennecessary to additionally or solely advance the magazine by one step.These requirements apply to partially and completely automated systemsand are adapted to the respective field of application.

The integration of automatic drives in the measuring instrument isprovided in some fields of application which require a complex transportof test strips due to special measuring procedures. For example suchmeasuring procedures are used to calculate errors in an analyteconcentration and determine the so-called blank value of a test elementamong others. Such a procedure is described in the document US2005054082A1, which is hereby incorporated by reference. For the blankdetermination the test element is firstly transported into a measuringposition in which the blank value of the test element is measured.Subsequently the test element is ejected so that the user can apply asample to the test element. The test element is again positioned at themeasurement site and an analyte concentration of the sample is measured.

Analytical systems are described in the prior art which use severalmechanisms for transporting test elements and transport the test elementto a position provided for measurement or for other process steps. Thepositioning of the actual detection area relative to the measuringsystem or to other process factors is promoted by a high precision ofthe drive components and by low manufacturing tolerances of the testelements. In conventional methods such drives are very complicated andexpensive and for example employ servomotors or low-tolerance gearunits. Currently known analytical systems that are subject tolarge-scale manufacturing of the test element can also be required tomeet high demands on accuracy to enable the mechanical system toreliably transport and position the test element relative to themeasuring system. The mechanical system used is usually very complex.

The document U.S. Pat. No. 6,475,436 B1, which is hereby incorporated byreference discloses an instrument mechanism that is used in ananalytical instrument to transport and advance a test strip magazine byone step. For this purpose a magazine chamber is rotated into a positionsuch that a plunger can be inserted into the strip storage pack and pushout a test strip from the storage pack until the test field of the stripis positioned above the optical measuring system. Subsequently themagazine is advanced by one step. An electrical motor is used to drivethe test strip and the magazine. The optical system is accommodated in aflap of the instrument and is positioned there to an accuracy of lessthan 1/10 mm. This requires many components and joins with lowtolerances. Furthermore high demands are made on the manufacturingtolerances of the test strips. In operation the drive system proves tobe loud and the operating speed is mediocre. Moreover the drive systemsare so large that it is difficult to achieve a compact design of theanalytical system which is especially desirable in the home monitoringfield.

In order to promote the operability of the systems, the drive unitsadditionally require lubricants which can contaminate the interior ofthe instrument housing and can for example be deposited on the testelements as a result of fraying processes. However, especially with thecommercial analytical systems high demands are often made on the storageof test elements which require a constant and especially dryenvironment. Consequently such contamination results in an impairment ofthe measuring results especially in the case of test elements that aresensitive to moisture and contamination.

Currently known transport units may often only allow movement along onedirection of movement. However, when using test element magazines it isoften desirable to return the test elements to the cassettes. Therecassetting of used test elements can simplify the handling of theanalytical system in a user-friendly manner. However, this requires thatthe test elements can be transported in different directions ofmovement. But, a transport in different directions of movement canrequire a complicated additional transport unit.

SUMMARY

According to the present invention a system and a method fortransporting test elements is provided. The system and method providepositioning of the test element relative to the measuring system andenable magazine handling. This provides that a drive system could behandled in a flexible manner without requiring considerable additionalexpenditure. The system can as small and compact so that it can also beused expediently in analytical systems that are designed to be spacesaving for home monitoring. Contamination of the analytical system by atransport unit should be avoided. The system can also be integrated intobattery-operated analytical systems.

According to the present invention an analytical system is provided. Thesystem comprises a detection unit for detecting at least one signal thathas been changed by an analyte in a sample and an evaluation unit todetermine at least one analyte in the sample based on the at least onesignal and a transport unit with a contact area. The contact area issuitable for directly or indirectly contacting the analytical systemwith a test element on which the sample can be applied. The transportunit comprises at least one piezoelectric element which vibrates thecontact area of the transport unit and the test element is transportedalong a defined transport path in the analytical system as soon as thecontact area of the transport unit is directly or indirectly contactedwith a test element and the contact area is vibrated by the at least onepiezoelectric element.

According to the present invention a method for transporting a testelement in an analytical system is provided. The method comprisescontacting a test element directly or indirectly with a contact area ofa transport unit in an analytical system, and prior thereto orsubsequently, activating a piezoelectric element of the transport unitsuch that the contact area of the transport unit is vibrated,transporting the test element due to the vibrated contact area along apredetermined transport path in the analytical system and stopping thetransport process of the test element such that the test element ispositioned at a predetermined site in the analytical system.

According to the present invention an analytical system for determiningan analyte in a sample is provided. The system comprises a detectionunit for detecting at least one signal that has been changed by ananalyte in a sample, an, evaluation unit to determine at least oneanalyte in the sample based on the at least one signal, and a transportunit with a contact area. The contact area is suitable for direct orindirect contact with a test element on which the sample can be applied.The transport unit comprises at least one piezoelectric element whichvibrates the contact area of the transport unit. The test element istransported along a defined transport path in the analytical system assoon as the contact area of the transport unit is directly or indirectlycontacted with a test element and the contact area is vibrated by the atleast one piezoelectric element. The transport of the test element isformed to be stopped such that the test element is positioned at apredetermined site in the analytical system.

According to the present invention, a method for controlling a transportunit in an analytical system is provided. The method comprisescontacting a test element directly or indirectly by means of a testelement carrier with a transport unit of an analytical system, thetransport unit being able to transport the test element along atransport path in the analytical system, transporting the test elementalong the transport path, irradiating the test element or the testelement carrier in a first wavelength range with a light source which islocated along the transport path, and detecting an optical change whichis due to the test element or the test element carrier wherein thetransport unit in the analytical system is controlled on the basis ofthe detected optical change.

According to the present invention a system for controlling a testelement transport is provided. The system comprises a transport unitwhich is able to transport a test element along a transport path withinan analytical system either directly or indirectly by means of a testelement carrier, a light source which is located in the analyticalsystem along the transport path such that a test element or test elementcarrier which is transported along the transport path is irradiated in afirst wavelength range and a detector for detecting an optical changewhich is caused by the test element or the test element carrier. Thetransport unit is contacted with the detector and the transport unit iscontrolled as a function of the signal detected by the detector.

These and other features of the present invention will be more fullyunderstood from the following detailed description of the inventiontaken together with the accompanying claims. It is noted that the scopeof the claims is defined by the recitations therein and not by thespecific discussion of the features set forth in the presentdescription.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is further elucidated in the following to illustrate theinvention.

FIG. 1: Bar-shaped drive element with two piezoelectric elements.

FIG. 2: Tubular piezoelectric drive element.

FIG. 3: Piezoactive element with drive rods.

FIG. 4: Analytical system with a piezoelectric motor and test elements.

FIG. 5: Drum-shaped test strip magazine with piezomotor.

FIG. 6: Test strip tape.

FIG. 7: Decrease in reflectance during test strip transport at 452 nm.

FIG. 8: Decrease in reflectance during test strip transport due todetection of a black bar.

FIG. 9: Test strip with various illumination zones.

Skilled artisans appreciate that elements in the figures are illustratedfor simplicity and clarity and have not necessarily been drawn to scale.For example, the dimensions of some of the elements in the figures maybe exaggerated relative to other elements to help improve understandingof the embodiment(s) of the present invention.

In order that the invention may be more readily understood, reference ismade to the following examples, which are intended to illustrate theinvention, but not limit the scope thereof.

DETAILIED DESCRIPTION

The invention concerns the use of piezoelectric drives for the direct orindirect movement of test elements within a diagnostic instrument inorder for example to position a test element relative to a detectionunit, to remove and return test elements in a magazine and as anadvancing mechanism for a magazine to mention only a few applications.The integration of a piezoelectric motor enables a flexible andcomfortable automatic handling of test elements in an analytical systemwhile substantially reducing motor noises, contamination etc.

The invention comprises an analytical system for determining an analytein a sample. The analytical system is used to analyse a test elementwhich has a carrier and an evaluation area on which a sample is applied.The test element is positioned in the analytical system such that atleast one signal is detected by a detection unit of the system wherebysaid signal is changed depending on the sample applied to the testelement. An evaluation unit of the analytical system is used todetermine an analyte in the sample based on the signal. The analyticalsystem also comprises a transport unit with a contact area in order todirectly or indirectly contact the analytical system with a testelement.

In this context a direct contact is for example when the test elementcarrier rests directly on the contact area of the transport unit. If, incontrast, the contact of the test element is indirect, the contact areaof the transport unit firstly contacts an instrument component that isto be transported which acts as a transport carriage for the testelement. Such a transport carriage can for example be a support area forthe test element in the analytical system. Furthermore the indirectcontact of the test element can for example be achieved in the form of amagazine housing which is in turn directly in contact with the contactarea or indirectly in contact with the contact area via a transportcarriage.

Stepping of the magazine results in a transport of the test element. Inorder to transport the test element, the transport unit has at least onepiezoelectric element which vibrates the contact area of the transportunit. If the contact area of the transport unit is vibrated by the atleast one piezoelectric element, the test element is transported along adefined transport path in the analytical system as soon as the contactarea of the transport unit makes direct or indirect contact with thetest element. If the direct or indirect contact between the contact areaand the test element is interrupted or the vibration of the contact areais stopped, the transport of the test element is halted and the testelement is positioned in a fixed position in the analytical system.

According to the invention a piezoelectric drive is used in the systemas a drive for the transport unit such that the contact area of thetransport unit is vibrated in such a manner that the contact areaexecutes a resonance vibration. As a result of the resonance vibration(which will be explained in more detail in the following) points on thesurface of the contact area make elliptical movements. If another bodysuch as a test element contacts these points (contact points), the testelement is at least partly conveyed further along a defined transportpath in the analytical system. In this manner the body to be transportedcan be directly conveyed or indirectly conveyed by means of anadditional component of the transport unit.

Hence within the sense of the invention the transport unit can beunderstood as a piezoelectric motor where the object to be transportedwhich makes direct contact with the contact area, is itself a part ofthe piezomotor. Consequently if, for example, the test element restsdirectly on the contact area, the test element is a component of themotor and the piezoelectric motor comprises a disposable element. Thisis for example also the case when the contact area of the transport unitis directly contacted with a magazine housing which is also provided asa disposable article in the analytical system. It is of course alsoconceivable that an additional component of the transport unit e.g. atransport carriage, as already described, is provided as anon-exchangeable unit for indirectly contacting the test element or amagazine, and the piezoelectric motor contains no disposable elements.

The use of a piezodrive in an analytical system enables the transportunit to be integrated into the analytical system in a small and compactmanner. In this connection the transport unit according to the inventionenables an integration of the piezoelectric motor in or in the vicinityof a magazine housing without impairing the quality of the stored testelements by for example lubricant deposits. A compact design of theanalytical system in which the test elements and motor are arrangedspatially next to one another can be achieved according to the inventionsince the transport unit does not need lubricants due to its piezomotor.Moreover, the constant and dry conditions for storing test elements areparticularly suitable for operating a piezomotor. This is primarily dueto the fact that defined frictional and static frictional forces actunder constant environmental conditions. Another characteristic of thedrive is that large forces and moments are already generated at lowspeeds.

Furthermore it enables rapid changes in movement in the analyticalsystem in which one direction of movement is rapidly and preciselychanged or the test element is brought to a standstill. In thisconnection the standstill of the element that is in contact with thecontact area takes place essentially without play in which case amaximal force (moment) acts on the element when it is at a standstilldue to static frictional forces. Reversal of the direction of movementallows a flexible handling and the transport unit can even beconstructed with a few components.

The general principle of a piezoelectric drive is known and describede.g. in Ultrasonic Motors—Theory and Application by S. Ueha and Y.Tomikawa; Oxford Science Publication, which is hereby incorporated byreference. The principle is described for illustration purposes in thefollowing on the basis of an example.

The operating principle of a piezomotor is illustrated using a lineardrive as an example without being limited thereto. A linear driveconsists for example of a beam. The beam is made of a material of highrigidity and low intrinsic dampening, a non-limiting example of which isa metal, and carries a piezoactive element at each of the two ends. Ifalternating voltage is applied to the first piezoactive element suchthat the beam is made to vibrate in resonance, a standing waveconsisting of longitudinal oscillations is generated in the beam. As aresult of the longitudinal oscillations of the beam, the beam iscontracted laterally at the sites which are being stretched and it isextended laterally at the compressed sites. As a result a point on thesurface of the beam which is also referred to as a contact point withinthe scope of the invention, makes a small lateral and longitudinalmovement relative to the axis of the beam due to the oscillations andits trajectory follows an elliptical path.

In order to transport a test element the test element in the describedexample is pressed directly onto the contact area. In the case of a teststrip for a blood sugar determination it is usually a flat object whichis mainly composed of a carrier foil made of plastic. If the bar is nowvibrated by the piezoelectric element, the carrier foil makes contactwith the contact points on the surface of the contact area. The carrierfoil and hence the test element firstly follow the movement of thecontact points due to the frictional forces acting between the carrierfoil and contact area. However, for a short period in which thedirection of movement of the contact points along the trajectory isreversed, the test element loses contact with the contact area due toits mass inertia and retains its state of movement before it is againtransported further due to the acting forces. Hence the test elementperforms a uniform movement despite the forces that act intermittently.If the vibration frequency and amplitude are adjusted according to theproperties of the element to be transported, the test element istransported along the defined direction of movement. The test element ismoved until the vibration of the beam is stopped or contact between thecontact area and carrier foil is permanently interrupted. If thevibration of the beam is stopped, the dynamic contact between the testelement and contact area becomes a static contact which holds the testelement in the position it has assumed due to static frictional forces.Consequently the frictional forces acting during the transport processare a fraction of the static frictional force which acts between thetest element and contact area when the transport unit is at astandstill.

In an embodiment of the invention, the contact area of the beam and thecarrier foil of the test element are designed such that when the testelement is in permanent contact with the contact area of the beam theacting static frictional moment is sufficiently large to ensure a securepositioning of the test element at a site in the analytical system. Thestatic frictional moment is about 1.5 times the drive moment of thepiezomotor in order to prevent a slipping of the test element as soon asthe transport unit is in a resting state, for example during themeasuring process.

If a voltage is also fed to the second piezoactive element the beam canonly vibrate along the area that is enclosed by the piezoelectricelements thus changing the length of the standing wave and consequentlythe resonance frequency of the beam.

Depending on whether current is applied to the piezoceramic stack incommon mode or push-pull mode, the contact points execute a clockwise oranti-clockwise trajectory which, depending on the direction of rotationof the trajectory, transports the test element along a positive ornegative direction of movement. The analytical system comprisespiezoelectric elements that can be electronically actuated independentlyof one another so that the direction of transport along a spatial axiscan be reversed by actuating the piezoelectric elements in a common orpush-pull mode.

Furthermore it is possible to achieve a linear movement of an element tobe transported by means of a standing bending wave as elucidated in moredetail in the following description. An intermittent drive force canthen be generated by placing a short tappet on the beam. The directionof movement can be turned round by changing between different resonancefrequencies.

A flexible change in the transport device is an advantage especially inanalytical systems that have to perform complex movement processes dueto an automated measuring process. As already described, an example ofthis is blank measurements in which the test strip is moved severaltimes towards and away from the measuring system, recassetting, magazinetransport etc.

Numerous applications of the system of the present invention areconceivable due to the ability to reverse the transport direction of thetest element. In an embodiment the test element can be transported andpositioned relative to the detection unit before and/or after sampleapplication, and after a measurement the test element can be transportedback to the starting position. Also, a test element can be transportedback into a magazine by a transport unit after a sample analysis forrestorage. Furthermore it is also conceivable that, after measurement ofthe test element, an additional transport unit transports it to a secondmeasuring position so that several measurements are carried out on thetest strip within an analytical system. In general there is nolimitation to the number of additional transport units in an analyticalsystem. In this context the transport units can be used to position thetest element relative to a detection unit for another measurement and,as already described, for restorage, ejecting the test strip, thestepwise advance of a magazine housing or test strip tape etc.

If the transport unit according to the invention is for example used totransport individual test elements or several test elements, thepiezoelectric element is connected in an embodiment with a detectorwhich enables a control of the piezoelectric element. An individual testelement is for example registered by a detector at one site in theanalytical system where a change in reflectance or transmission isdetected by irradiating the test element. The detected change inreflectance or transmission generates a signal for controlling thepiezoelectric motor. In this connection, the power supply to thepiezoelectric elements can be interrupted so that an optical change dueto the test element can be detected in the analytical system. If, forexample, the test element transport is stopped immediately afterdetection of the test element, this enables an exact positioning of atest element at a defined position in the analytical system.

In principle, the control of test element transport can be based on achange in reflectance or transmission detected by a detectorindependently of the design of the transport unit. In this case the testelement can be directly or indirectly transported for example in amagazine housing by means of a piezoelectric motor, electric motors orother drives that are well-known in the prior art. In general suchcontrol of test element transport is not limited to any specific driveunit for the transport unit but must essentially only comprisecontacting the transport unit with an optical detector to generate asignal for controlling the transport unit and thus the transport of thetest element which is dependent on an optically detected change.Furthermore, control of the transport unit can for example be based onthe detection of reflected, transmitted or luminescent radiation so thatthe invention is not limited to any specific optical detection. Theinvention is illustrated in the following using the detection ofreflected or transmitted radiation as an example whereby the examplesare not to be understood as being a limitation. In this connection achange in an optically detectable radiation is detected according to theinvention which for example is referred to as a change in reflectance ortransmission etc. The radiation detected in this manner is referred toas a detection value.

Hence the invention also concerns a method for controlling a transportunit in an analytical system. In an embodiment of the invention, a testelement is directly positioned on a transport unit of an analyticalsystem so that the test element can be directly transported by thetransport unit. However, it is also conceivable that one or more testelements are positioned on a transport carriage, as already described,which is conveyed by the transport unit and thus the test elements areindirectly transported in the sense of the invention. For example such atransport carriage or test element carrier is a magazine housing whichcontains a plurality of test elements and the transport unit advancesthe magazine e.g. in a stepwise manner. Hence the transport unit movesthe test element directly or indirectly along a transport path in theanalytical system in which a light source is located. The test elementor test element carrier is irradiated with light in a first wavelengthrange and an optical change due to the test element or the transportcarriage or the test element carrier is detected. The transport unit iscontrolled on the basis of the detected light. Furthermore the inventionconcerns a system for controlling test strip transport which comprises atransport unit for the direct or indirect transport of a test elementalong a transport path. The system has a light source which is locatedalong the transport path and which irradiates the test element or thetransport carriage in a first wavelength range. A detector for detectingoptical changes caused by the test element or the transport carriage iscontacted with a transport unit so that the transport unit is controlledon the basis of light detected by the detector.

If the test element is transported indirectly by a transport carriage, amark attached to the transport carriage is detected by reflectionphotometry. If, in contrast, the test element is transported directly bythe transport unit, the test element can also be measured on the basisof transmission or luminescence radiation in addition to detection ofradiation reflected from the test element. In this connection theoptical change caused by the test element can for example be detected onthe basis of radiation reflected or transmitted by the carrier foil ofthe test element. Such a signal is then detected as soon as the testelement crosses the light beam of a detection unit along the transportpath in order to control the transport unit. Furthermore embodiments areconceivable in which a recess/hole in the test element is used forpositioning. For example during the period in which the test element isdetected, test element transport is stopped after an optical changecaused by the hole is detected. Especially in the case of transmissionmeasurement, detection of a hole in the test element allows a simpleconstruction of the detection unit which does not detect light until thehole of the test element is located between the light emitter anddetector. If, on the other hand, the carrier foil or other areas thatare impermeable to light are located between the light emitter anddetector, the optical path of the optical system is blocked and no lightcan be detected by the detector. Similar embodiments can of course alsobe realized for other measuring procedures such as reflectancemeasurement. However, in an embodiment of the invention the change inthe radiation that is reflected or transmitted by the test element iscaused by a test field of the test element which is provided foranalysing a sample. For this purpose the test field has a differentreflection or transmission value than the carrier material of the testelement and this value is detected in order to control the transportunit. During transport of the test element along a detection unit whichis used to control the drive unit, the detector firstly registers afirst reflection, luminescence or transmission value at the start of thetransport process. The first value registered by the detector is firstlydue to the carrier material, e.g. a carrier foil of the test element andchanges during the forward movement as soon as the test field of thetest element is registered by the detection unit. The optically detectedchanges generated in this manner are the basis for controlling thetransport unit which for example is stopped immediately after the signalexceeds or falls below a specified threshold value.

The method for controlling the drive unit is in general not limited tothe detection of a threshold value. Thus for example control can also bebased on registering a curve time-course of the detected values and thevalues derived therefrom. It is also possible to detect only one valueor only to register whether it is below or above a value. Hence themethod according to the invention for controlling a drive unit is notlimited to the detection of certain values but can be varied asrequired.

The detection unit for controlling the transport process for examplecomprises one or more additional light sources and a detector which arearranged along the transport path and form a detection unit. Usually anLED can be used for such a light source which emits light in a spectralrange of <600 nm, and in an another embodiment <500 nm. Investigationswith conventional test elements have shown that the difference inreflectance between a conventional test carrier of a test strip and atest field is largest within this wavelength range. Of course otherspectral ranges may prove to be suitable depending on the test elementthat is used and hence the invention is not limited to any specificwavelength range. Hence, in the described example the analytical systemhas another detection unit to control the transport unit in addition toa first detection unit which measures an analyte on the test element.

The position of the detection units relative to one another within theanalytical instrument is selected such that when the transport unit ishalted, the test field of the test element is directly positioned in adesired manner relative to the measuring optics of the first detectionunit to allow measurement and evaluation of the test field. Within thescope of the invention the position within the analytical system of thetest element on which an analysis of the test field is to be carried outis referred to as the detection position which in the described exampleis located on the transport path of the test element in the analyticalsystem. Hence within the meaning of the invention a positioning of atest element at the detection position enables an essentially error-freeevaluation of the test element in an evaluation area of the test fieldthat is completely covered by the first detection unit.

If the test field is directly detected in order to control the transportunit, an additional detection unit for controlling the transport unit inthe analytical system can be omitted. The first detection unit that isalready integrated into the analytical system to evaluate the test fieldis then used to control the transport unit. Thus an additional lightsource and detector are not required which simplifies the instrumentdesign and reduces costs. Of course combinations of the describedembodiments are also conceivable in which for example only one detectoris provided in the system but different light sources are used for theinitial detection of the test field or analysis of the test field. Inprinciple the system according to the invention is not limited to anyspecific test element or detection unit for determining an analyte sothat a wide variety of known analytical methods in the prior art can beused. For example electrochemical measurements etc. can also be used toevaluate a test field in which case an additional optical detection unitmay be required to control the test element transport.

If only one detection unit is used in the analytical instrument in anembodiment, the detection unit of the analytical system firstly detectsthe position of the test field to stop the transport of the test elementimmediately after registering the test field. Subsequently ananalyte-specific signal from the test field of the test element ismeasured with the same detection unit in another wavelength range. Thedescribed method promotes an exact positioning of the test fieldrelative to the detection unit that is also used to evaluate the testfield. Thus, the optical measuring system is accurately positioned.

If, in another embodiment, the test field is detected by the firstdetection unit in order to control the transport unit but using the samewavelength range that was also used to evaluate an analyte-specificsignal, this may under certain circumstances unfavourably influence themeasuring accuracy of the method. This is especially due to the factthat firstly a first reflectance change is generated by the test fieldto control the transport unit before sample is applied to the testfield. After sample application, an analyte-specific second reflectancechange is generated which is used to evaluate an analyte concentration.Hence the second change in reflectance that is available for evaluatingthe analyte signal is reduced by the magnitude of the first reflectancechange. Such a reduction in the reflectance change may lead toinaccuracies in the analyte determination depending on the field ofapplication and the analyte to be determined. Consequently detection ofthe test field to control the transport unit in a second wavelengthrange in which no analyte determination takes place can, as alreadydescribed, improve the accuracy of the analysis.

Furthermore it is also possible to use luminescent substances in thetest field to detect the position of the test element. The excitedluminescence radiation which is for example excited in the samewavelength range in which the analyte is measured is then used to detectthe test field. However, the luminescent radiation can also be detectedin a wavelength range that is different from that of the analyte signal.Consequently, depending on the test element that is used, it is alsopossible to detect the test field without requiring different wavelengthranges to irradiate the test field while at the same time ensuring anadequate analytical accuracy.

In addition to the detection of the test field for controlling testelement transport, it is also possible to provide a mark e.g. in theform of a coloured bar to detect and control test element transport.Hence it is possible to optically detect a test element or transportcarriage in many different ways. The use of additional marks may beused, for example, when the test elements are indirectly transported forexample when there is a magazine transport unit to advance the magazinein a stepwise manner. In this case marks attached to the magazinehousing can be used to detect the position of the magazine and thuspromote an exact positioning of the magazine housing relative to otherinstrument components (e.g. drive plunger for test element/lancets etc.)that interact with the magazine housing.

The use of an additional mark directly on the test element allows thatthe magnitude of a reflectance difference can be selected depending forexample on the colour of the mark without needing to adapt the lightsource in the analytical instrument. On the other hand the position ofthe mark on the test element allows a free selection of a desiredpositioning of the mark relative to the test field and thus relative toinstrument components in the analytical system. This enables a versatileintegration of the method/system according to the invention into thedesign of conventional analytical instruments. If the mark is located ona test element on the far side of the test field relative to thedirection of insertion, embodiments are conceivable in which firstly thetest field is detected and as a result of the detected difference inreflection the test strip transport is firstly slowed down. Transport isthen stopped as soon as the mark results in a second reflectancedifference. Hence the use of an additional mark allows a versatileintegration of the system according to the invention into conventionalanalytical instruments as well as numerous embodiments for controllingthe transport unit. The control of the transport unit can in principlebe based on simple or complex processes. In addition to the possibilityof immediately stopping the transport after detection of a transmissionor reflectance difference etc., it is possible to trigger a transportstop for example only after a defined time interval after detection of apredetermined value. Furthermore, it is also possible to permanentlymonitor the positioning of the test element during the measuring processby the analytical system. For example if a test element that haspreviously been exactly positioned gets out of place during themeasuring procedure, for example due to an external jolt, this incorrectpositioning can be detected by the system in an embodiment. If, forexample, a deviation from a threshold value is detected, the position ofthe test element can be corrected until a predefined threshold value isagain registered by the detector by means of an appropriate control andactivation of the transport unit. This promotes, among others, that thetest field is only evaluated when the test element is correctlypositioned.

Hence the method according to the invention can encompass a wide varietyof embodiments which also include complex transport and controlprocesses. In this context it is equally possible to detect severalthreshold values which result in a transport process at various speedsdown to a transport stop as well as an initiation of the transportprocess.

The described control mechanisms for test strip transport promote amongothers an exact positioning of a test element relative to the detectionunit so that a test field can be reliably detected for the analysis of asample. Hence an exact positioning of the test element within theanalytical instrument can be promoted without making high demands on themanufacturing tolerances of an analytical instrument and a test element.Moreover use of an additional mark on the test element allows largertolerances for the positioning of one or more detection units and ofother instrument components within the analytical instrument as well asfor the test element production itself. Especially in the case of testelements that are manufactured in large numbers as disposable articles,a large manufacturing tolerance allows a considerable simplification ofthe manufacturing process and thus an economic production. Differencesin tolerance due to the manufacturing process can be directlycompensated during the measurement process by the inventive control ofthe test strip transport. This enables considerable cost savingsespecially for single-use articles.

In addition to detecting the test element at one site in the analyticalsystem, it is also conceivable that a holder in the analytical systemstops the transport of the test element. Such a holding device can forexample be a simple mechanical barrier in the form of a stop.Furthermore it is also possible for the transport process to be stoppedafter a predetermined time. In this case the piezoelectric transportunit facilitates an exact calculation of the transport path per unit oftime so that after a defined operating time for the transport unit anexact positioning of the test element is also possible.

The transport unit can for example be activated by a contact elementwhich activates the transport unit when the test element makes contactwith the contact area of the transport unit. Of course any otheractivation mechanisms are conceivable such as a separate actuation ofthe transport unit by a control button. The invention also comprises amethod for transporting a test element in an analytical system. In thismethod the carrier of a test element is contacted with a contact area ofa transport unit in an analytical system. A piezoelectric element of thetransport unit vibrates the contact area of the transport unit. If thecarrier of the test element has made contact with the contact area, thetest element is transported in the analytical system along apredetermined transport path. The transport process of the test elementis stopped at a predetermined site at which the test element is to bepositioned to allow a positioning of the test element.

FIG. 1 shows the major components of a transport unit 1. The transportunit comprises a beam made of brass 4 to which a stack of piezoceramicplates 2 is attached to each end. Each of the piezoceramic plates has aseparate electrical connection 3. Furthermore the ceramic plates arearranged at the respective ends of the beam 4 in such a manner that astanding wave comprising a longitudinal oscillation is generated in thebeam when an alternating voltage is applied to one of the two piezostacks, the length of the areas 4 a of the beam that are distal to thepiezo stack being chosen such that the piezo stack lies in the antinodeof the standing wave that is to be generated. As a result of the lateralcontraction of the beam associated with the longitudinal oscillation, apoint on the surface of the beam executes an elliptical trajectory path.If current is now applied to the second piezo stack, the wave of thebeam can no longer extend beyond the second piezo stack into the area 4a. As a result of applying current to the second piezo stack the beamnow behaves as if it has been effectively clamped in the analyticalsystem by the piezoceramic plates. If voltage is synchronously appliedto both piezo stacks, points on the surface of the beam form acounterclockwise trajectory. If, on the other hand, current is appliedto the second piezo stack in a push-pull manner, the standing wave thatis generated is shifted by half a wavelength. A point on the surfacewhich previously had a counterclockwise trajectory now has a clockwisetrajectory which reverses the direction of transport of a test elementconveyed by means of friction on the point. Consequently, it is possibleto change the transport direction along the beam 4 by supplying powerseparately to the piezo elements and by a suitable selection of thecurrent. This for example enables an analytical system to transport atest element from one support surface to the measuring system and toreverse the transport process after measurement such that the testelement can be removed again by the user at a readily accessible site.

FIG. 2 (a-c) shows a cylindrical rod made of piezoceramic 4 which iscovered with four electrodes 2. Each of the electrodes covers about ¼ ofthe circumference of the cylindrical rod and extends over the entirelength of the rod. An electrical contact is made with the electrodes viathe connectors 3. The electrical contacts shown in FIG. 2 a result in apolarization of the ceramic which is shown by the dashed arrows. If analternating voltage is applied to two opposing electrodes, the rodperforms a bending oscillation (see FIG. 2 c).

If an alternating voltage with a 90° phase difference is fed to theother two electrodes, the rod performs a revolving bending oscillationwhich results in an elliptical trajectory of a surface point on thesurface of the rod in the area of the maximum amplitude.

An object that is pressed against this point on the rod will be carriedalong due to the frictional forces acting on it as already described.The direction of movement is reversed by changing the phase differencebetween the voltages from +90 to −90°.

FIG. 3 a shows a transport unit 1 with a drive plunger. The piezoactiveelement 2 is contacted with a beam 4. Drive rods 7 are positioned on thebeam 4 which improve the transport property of the transport unit. Ifthe beam 4 is vibrated by the piezoactive element, the beam performs abending oscillation and a bending standing wave 8 is excited in the beamas shown in FIG. 3 b. As already described the vibration 9 of the beam 4results in an elliptical movement of contact points on the surface. Ifdrive rods 7 are present on the contact points of the surface, thetrajectory of the contact points that are now on the surface of thedrive rod is enlarged depending on the length of the drive rod 7. Theenlarged trajectory of the contact points improves the transport of anelement 10 to be transported which rests on the drive rods. For examplesuch a transport unit can generate forces in the range of 5 Newtons anda speed of 80 mm/s at a resonance frequency of 22.31 kHz. In this casethe direction of movement is changed by applying a different resonancefrequency.

FIG. 4 shows an analytical system with a transport unit in which a teststrip is directly driven by piezoelectric elements.

For this a test strip 15 is firstly pushed out of a magazine 11 alongthe direction of movement 14 by a plunger 12 until the test stripcontacts the transport unit. The design of the transport unit isessentially similar to the transport unit in FIG. 3 a and has two beams4 that are equipped with drive rods 7. The beams 4 are connected topiezoactive elements 2 and are vibrated by them as soon as the transportunit is activated. The beams 4 and the piezoactive elements 2 arecountertensioned and positioned by spring elements 16. When the teststrip 15 comes into contact with the transport unit 1, the strip ispicked up by the drive rods 7. The drive rods excited by thepiezoelements on the outer sides of the beams 4 vibrate to such anextent that contact points on the surface of the drive rods performelliptical movements which move the test element 15 along the transportpath. In principle the transport of the strips can be stopped at anypositions in the analytical system. In the example shown a test zone 15a of the test element 15 is detected at one site in the analyticalsystem to control the transport unit and the transport unit is stoppedas soon as the test zone 15 a has been detected. A detection device 17which is also used for the optical analysis of the test zone 15 a isused to detect the test zone 15 a. If the transport of the test strip isstopped immediately after detection of the test zone 15 a, this promotesthat the test zone 15 a is correctly positioned relative to thedetection device 17. Errors in the analysis of a sample in the test zonewhich are caused by an incorrect positioning of the strip can thus beavoided. The detection device 17 consists essentially of a light source18 to irradiate the test zone and a sensor 19 which detects radiationreflected by the test zone. When the transport of the test element isstopped, the spring elements 16 promote an exact positioning of thestrip at the target site in addition to the static frictional forceacting between the contact area of the drive unit and the test strip. Ifthe frequency applied to the piezoactive elements 2 is changed, it ispossible to reverse the direction of transport of the test element whichenables the strip to be transported backwards. This enables the teststrip to be placed back into the magazine 11 for storage.

In addition to the transport of a strip-shaped test element it is alsopossible for the transport unit to move the strip cassettes that areused to store test strips. For example a cylindrical test strip cassettecan be rotated by a drive such that successive test strips can beremoved from the cassette and a stepping of a test strip magazine can beachieved. In this case it has proven to be advantageous when themagazine does not directly contact the contact area of the transportunit since the magazine housing is often contaminated by for examplefats due to handling steps. Such contamination can alter the frictionalmoment between the contact area and the housing to such an extent thatit impairs the ability of the piezomotor to function. It has thereforeproven to advantageous to drive the magazine housing by an additionalinstrument component which functions as a transport carriage in thepiezomotor.

If a test strip is directly transported instead of the magazine housing,it is often possible to omit an additional transport carriage since thetest element can be removed dust-free and fat-free from a cassette as aresult of manufacturing processes. If test elements are notautomatically handled by the analytical system so that the user has tomanually insert the test element into the instrument, the use of atransport carriage may prove to be of advantage in this case.

FIG. 5 shows a drive for a drum-shaped test strip magazine as known fromthe prior art and which is used by the Roche Company in the ACCUCHECK®Compact analytical system. The magazine 11 has a plurality of testelements (not shown) which are stored in individual chambers of themagazine. In order not to impair the quality of the test elements, themagazine is sealed with a foil at the ends of the drum. In addition themagazine has an additional drum 21 in its upper portion which closes theupper end of the magazine either alone or in addition to a foil. Inorder to achieve a compact design of the analytical instrument, thepiezomotor is integrated into the drum 21 in order to advance themagazine. The drum and hence the magazine are mounted and positionedcentrally on an axis 25 in the analytical system. A ring 2 made ofpiezoelectric material which is connected to lamellae 23 which form thecontact area of the transport unit is positioned inside the drum. Thelamellae 23 are pretensioned as a result of the intrinsic elasticity ofthe lamellae 23 which promote contact between the transport surface andthe inner side 21 a of the drum 21. The lamellae 23 are bent to such anextent that the lamellae point semitangentially in one rotationdirection. If an alternating voltage is applied to the piezoelectricring 2, the lamellae are vibrated. If the frequency corresponds to theresonance frequency of the lamellae, contact points on the surface ofthe lamellae that are in contact with the inside of the drum 21 a forman elliptical trajectory. In accordance with the general principle thathas already been described this results in a transport of the drum suchthat the magazine housing is rotated about its axis 25. Furthermoreholding structures 24 are positioned in the drum interior so that thelamellae 23 and the piezoring 2 are themselves secured against rotation.A push rod 12 which has an external thread is present to eject the testelements from the drum. A rotor 27 which is driven by another piezomotor28 is screwed onto the thread. The piezomotor 28 is tubular and iscontacted with a mass electrode in the interior of the tube. Threeworking electrodes are attached (not shown) to the outer tube wall ofthe piezomotor 28. If a three-phase alternating voltage is applied tothe electrodes, an expansion oscillation is induced which generates arevolving wave movement at the end faces (contact area) of the tubularmotor which revolves the rotor 27. As a result the push rod 12 isscrewed forwards so that it can penetrate into the magazine through thehole 29 in the bottom of the drum. When the phase of the alternatingvoltage is reversed, the direction of rotation is reversed and the pushrod is retracted.

FIGS. 6 a and b show an analytical instrument in which a plurality oftest elements are arranged on a test strip tape. In this case the testelements are stored on a reel on which the test strip tape is wound.After a test element has been used, the used part of the tape is woundonto another reel according to the known principle in the prior artwhich is for example also used for audiotape cassettes. This enablestest elements that have been already used to be returned to themagazine. Analytical instruments which use the described test elementsare for example described in the documents WO US 02/18159 and EP 02 026242.4, which are each hereby incorporated by reference.

The reels 32 and 33 of the test tape are mounted on a hub in thecassette housing 31. The hub for the waste reel 33 has a carrierstructure into which the carrier element 34 engages at the side of theinstrument. The underside of the carrier element 34 is in the form of ahollow drum 21 in which for example a piezomotor consisting of apiezoring 2 and lamellae 23 is clamped. The lamellae 23 are bent in onedirection of rotation to promote that the motor is spring-clamped in thedrum. If alternating voltage is applied to the piezoring 2, the lamellae23 are vibrated similarly to the principle that has already been used inFIG. 5. This results in a rotation of the carrier element 35 resultingin a rotation of the waste reel 33 in a clockwise direction. Holdingstructures 24 are provided to prevent a rotation of the piezomotoritself. Of course the use of electromotors etc. is in principle alsopossible. However, the size and costs of the motor type have to bechecked for the respective field of application. In addition care mustbe taken that the test element is not contaminated due to lubricants orother deposits from the respective motor.

In order to convey test elements in the analytical system, thepiezomotor rotates the carrier element such that the waste reel 33 andconsequently the tape reel 38 is rotated and the test strip tape 32 iswound onto the reel 33 by a defined amount. The test strip transport issuch that a test field on a test strip tape is positioned above anoptical system 37 located in the instrument. An exact positioning of thetest element relative to the optical system is promoted by a staticfrictional force acting between the lamellae and carrier element asalready described. In addition deflection rollers 35 and a passive brakeof the tape reel 38 (not shown) promote a secure and stable guidance ofthe tape. The transport unit is controlled by the optical system in theinstrument. The transport is stopped for example as soon as the testfield can be registered by the optical system. Of course embodiments areconceivable with combinations of features that have already beendescribed such that for example an additional optical system can be usedor additional marks can be provided on the test strip tape. If a sample39 is applied to the test field positioned in this manner, an analyte inthe sample can be optically determined by means of the optical system37. Subsequently the used test field is wound onto the waste reel byadvancing the tape transport and is thus returned to the magazine. Thisallows a comfortable waste handling of used test elements.

Furthermore this enables a compact design of an analytical system sincethe piezomotor is in the direct vicinity of the test elements.

FIG. 7 shows an example of the curve time-course of measured reflectancevalues during test strip transport before sample application. Thetransport path [mm] is plotted versus the detected reflectance values(the reflectance was normalized against the reflectance value for thecolour white so that a relative reflectance value is shown in thegraphs). The test strip is for example transported by means of apiezoelectric motor. However, any other forms of drive units e.g.electromotors which are well known in the prior art are conceivable. AnLED which emits light in a range of 452 nm is used as a light source toirradiate the test element. The LED is integrated into the analyticalsystem in addition to the first detection unit for evaluating the testfield and is only used to detect the position of the test field. Forthis purpose the LED emits radiation in a wavelength range that is notused to measure an analyte. However, the light reflected by the testfield is detected by a detector of the detection unit so that anadditional detector is not needed. If the test element is transportedalong the transport path to the detection unit in order to measure thetest field, the test element carrier is firstly irradiated by theadditional light source in the analytical system. In the example shownthe test element comprises a white carrier foil which reflects lightalmost completely. This results in a reflectance value of 1 forradiation reflected by the carrier foil in a first region 46 of thecurve. After the test element has been transported by 1.5 mm thedetected reflectance value decreases in a second region 47 of the curveand reaches a minimum of ca. 0.25. In this position the test field ofthe test element is located above the detection unit in the analyticalinstrument where the measured reflectance value is generated by thedetection of the test field itself. In an embodiment, test striptransport is stopped at this position resulting in a positioning of thetest field above the detection unit. For example an immediate transportstop can be triggered when the reflectance value falls below a thresholdof <0.6.

Furthermore, in addition to controlling the test element transport onthe basis of threshold values, it is also possible to use complexcontrol mechanisms which for example firstly result in a slowing down ofthe test strip transport at a first decrease in reflectance. Finally,transport is stopped when a further predefined reflectance value isdetected. The initial deceleration of the transport enables a veryprecise control of the test element transport as already described andconsequently enables the test field to be exactly positioned relative tothe detection unit without making high demands on the manufacturingtolerances of the test element or of the analytical instrument.

FIG. 8 shows a reflectance curve during a test strip transport accordingto the example shown in FIG. 7 at a wavelength of 452 nm and 525 nm. Thecurves at different wavelengths are qualitatively identical so that theystart with a 100% reflectance when the white carrier foil of a testelement is detected. The reflectance decreases when the test field isdetected which has a plateau value of about 0.25 at a wavelength of 452nm so that a maximum difference in reflectance of 0.75 between thecarrier foil of the test element and the test field can be achieved. Ifthe measurement is made at a wavelength of 525 nm, a plateau value of0.6 is achieved when the test field is detected resulting in areflectance difference of 0.4. This plateau value is already achievedwith a transport path of about 2.5 mm. In the example shown thetransport process is not stopped after detecting the test field so thatthe test element transport is firstly continued until a secondreflectance difference is detected which is due to the black bar on thetest strip and occurs in a third region 48 of the curve. The black markdecreases the reflectance to a value of 0.1 which can initiate atransport stop as soon as the reflectance falls below a threshold valueof 0.15. This results in a corresponding change in reflectance comparedto the detection of the test field of ca. 0.5 for a measurement at 525nm. The described curves illustrate the different ways in which theinventive method can be adapted depending on the test element and theanalytical instrument. If the test strip is measured at 525 nm, there isa considerable difference in the reflectance between the test field andmark when a black mark is used on the test element and hence the use ofa black bar is recommended in the said wavelength range. If, incontrast, the measurement is carried out at 452 nm an additional mark isunnecessary since there is already a sufficiently pronounced differencein reflectance between the carrier foil and test field in thiswavelength range. However, this also shows that measurement of ananalyte-specific signal at 452 nm presumably would not give asatisfactory result. An analyte-specific absorbance of the light canonly result in a reflectance difference of no more than 0.2. However,the evaluation of an analyte concentration based on such a smalldifference in reflectance often proves to be erroneous and shouldtherefore be avoided. If, on the other hand, the test field isirradiated at a wavelength of 525 nm, a reflectance difference of 0.6remains which can be regarded as adequate to evaluate ananalyte-specific signal. If, however, a difference in reflectancebetween the carrier foil of the test element and the test field is notregarded to be of sufficient magnitude at a wavelength of 525 nm todetect the position of the test element, an additional black mark can beused as described in the example. In this manner the use of a singlelight source enables detection of the test element in order to detectits position in the analytical instrument and also allows the analysisof a sample with sufficient accuracy. Hence an additional light sourcein the analytical instrument is not needed.

FIGS. 9 a-9 d show examples of various embodiments of the method/systemaccording to the invention in which illumination zones are arrangeddifferently on a test strip. The resulting arrangements of lightemitters are selected as examples and show only a few possibleembodiments. Of course in principle any arrangements are possible whichgenerate an optically detectable change during test strip transport thusenabling control of the transport unit.

The test strip shown in FIG. 9 a has a white carrier foil and a testfield 45 which has a different colour. The zones 41, 42 and 43 that areshown represent the areas of the test element that are irradiated bythree different light sources in the analytical system and are measuredcorrespondingly. Within the scope of the invention these areas arereferred to as illumination zones. The areas of the test elementlabelled 42 and 43 are used to measure the analyte present in the testfield and are positioned in the middle of the test field which definesthe evaluation area of the test field. A measurement to detectunderdosing is additionally carried out in the area labelled 41 in amanner which is well-known in the prior art and is for example describedin US2004136871 A1, which is hereby incorporated by reference.

In principle the system can be extended according to needs in order tomeasure blank values, white values or black values as described inUS2005054082 A1 which is hereby incorporated by reference. Hence area 41is arranged on the test field 45 in a known manner, as used inconventional systems, and is an example of possible embodiments that areusually used to evaluate a test element. The control of test striptransport according to the invention is, however, independent of suchembodiments and hence only the illumination zones 44 which are usedaccording to the invention to control the transport unit, are varied inorder to illustrate the invention in FIGS. 9 a-d.

The illumination zones 44 shown in FIG. 9 a cover areas of the testfield as well as the carrier foil of the test strip. Hence measurementof the labelled area results in a change in reflectance that is based onradiation reflected from the carrier foil as well as from the testfield. A threshold value to control the transport process is adaptedaccording to the reflectance differences obtained in this manner. Whenthe values fall below a threshold value defined in this manner thisimmediately initiates a halting of test strip transport. After thetransport of the test strip has stopped, the test element is in anappropriate position to allow the evaluation area 41 of the test stripto be completely detected by the detection unit.

In FIG. 9 b the illumination zone 44 is arranged like that of FIG. 9 aso that areas of the carrier foil as well as of the test field aredetected. However, in this case the illumination zone is positioned atan outer edge of the test element. This prevents interference by a bloodsample applied to the test field which would result in anon-reproducible change in reflectance. This utilizes the fact that inthe example shown the blood is applied in a front region 50 of the testelement and the sample is conveyed exclusively into the middle of thetest field by means of a capillary gap. Hence the edge region of thetest field in which the illumination zone 44 is positioned does not comeinto contact with the sample. Consequently this promotes a reproducibledetection of a predetermined change in reflectance in a simple mannerwithout the risk of interfering effects by the sample application.

In FIG. 9 c the corresponding illumination zones 44 are arranged withinthe test field in an edge region that is not contaminated when thesample is applied. In comparison to FIG. 9 b the test field has twoillumination zones 44 that are irradiated by two LEDs in the analyticalsystem. Since both illumination zones are within the test field, areflectance value of the light reflected from the test field is detectedas a function of the wavelength that is used corresponding to the valuesshown in FIGS. 7 and 8. The respective threshold values are chosenaccordingly to control test strip transport whereby one utilizes thearrangement of the two illumination zones. When the test strip istransported a first change in reflectance is detected when the firstarea 44 of the test field is irradiated. This firstly results in aslowing down of test element transport. If a second change inreflectance is detected due to irradiation a second illumination zone inthe test field, the test element transport is stopped. The positions ofthe two illumination zones 44 within the test field are selected suchthat the evaluation area of the test field is between the twoillumination zones thus reliably ensuring a complete detection of theevaluation area 42, 43.

FIG. 9 d shows a test element with an additional mark 51 to control teststrip transport which extends over the whole width of the test elementin the form of a black bar. According to FIG. 8 test strip transport isstopped as soon as a change in reflectance caused by the detection ofthe mark is registered. Due to the spatial separation of the test fieldand the mark, two detection units are integrated into an analyticalsystem to measure the strip shown in FIG. 9 d. The mark on the testelement and the detection units are oriented relative to one another insuch a manner that the evaluation area of the test field is positionedabove the optical measuring system of the first detection unit as soonas the radiation reflected by the mark is detected by the seconddetection unit. An immediate stop of the test element transport thenleads to an exact positioning of the test field relative to the firstdetection unit.

In principle a variety of possibilities are conceivable for arranging anillumination zone 44 on a test strip to control test strip transport.The examples illustrate only a few embodiments which are examples of themany different possibilities whereby the illumination zones, theevaluation area of the test field and the light emitter or lightemitters and detectors can be appropriately matched to one another.

Having described the invention in detail and by reference to specificembodiments thereof, it will be apparent that modification andvariations are possible without departing from the scope of theinvention defined in the claims. More specifically, although someaspects of the present invention are identified herein, it iscontemplated that the present invention is not necessarily limed tothese one aspects of the invention.

1. Analytical system for determining an analyte in a sample, the systemcomprising a detection unit for detecting at least one signal that hasbeen changed by an analyte in a sample and an evaluation unit todetermine at least one analyte in the sample based on the at least onesignal and a transport unit with a contact area wherein the contact areais suitable for directly or indirectly contacting the analytical systemwith a test element on which the sample can be applied and the transportunit comprises at least one piezoelectric element which vibrates thecontact area of the transport unit and the test element is transportedalong a defined transport path in the analytical system as soon as thecontact area of the transport unit is directly or indirectly contactedwith a test element and the contact area is vibrated by the at least onepiezoelectric element.
 2. Analytical system as claimed in claim 1, whichis used to analyse the test element wherein the test element comprises acarrier and an evaluation area on which the sample is applied. 3.Analytical system as claimed in claim 1, in which the test element ispresent in a magazine housing.
 4. Analytical system as claimed in claim1, in which a detection site is located in the analytical system alongthe transport path.
 5. Analytical system as claimed in claim 1,comprising at least two piezoelectric elements that are electronicallyactuated independently of one another.
 6. Analytical system as claimedin claim 1, in which the piezoelectric element is contacted with adetector and the detector is used to control the at least onepiezoelectric element.
 7. Analytical system as claimed in claim 6, inwhich the detector is a component of the detection unit.
 8. Analyticalsystem as claimed in claim 6, in which the detector detects theevaluation area of a test element.
 9. Analytical system as claimed inclaim 2, in which the contact area of the transport unit and the carrierof the test element are made such that in a resting state of thetransport unit static frictional forces act between the contact area andthe carrier to such an extent that the test element is fixed in positionrelative to the transport unit.
 10. Analytical system as claimed inclaim 1, in which the transport unit has a contact sensor whichactivates the transport unit when the test element contacts the contactarea of the transport unit.
 11. Analytical system as claimed in claim 1,in which the transport unit causes a carrier element to rotate which issuitable for bearing and positioning a reel.
 12. Analytical system asclaimed in claim 11, which is suitable for using a test strip tape woundonto the reel.
 13. Method for transporting a test element in ananalytical system comprising contacting a test element directly orindirectly with a contact area of a transport unit in an analyticalsystem, and prior thereto or subsequently activating a piezoelectricelement of the transport unit such that the contact area of thetransport unit is vibrated, transporting the test element due to thevibrated contact area along a predetermined transport path in theanalytical system and stopping the transport process of the test elementsuch that the test element is positioned at a predetermined site in theanalytical system.
 14. Method as claimed in claim 13, in which the testelement is positioned relative to a detection site of a detection unitof the analytical system.
 15. Method as claimed in claim 13, in whichthe test element is returned into a magazine.
 16. Method as claimed inclaim 13, wherein the analytical system comprises a detection unit fordetecting at least one signal that has been changed by an analyte in asample and an evaluation unit to determine at least one analyte in thesample based on the at least one signal and the transport unit with thecontact area wherein the contact area is suitable for directly orindirectly contacting the analytical system with a test element on whichthe sample can be applied and the transport unit comprises at least onepiezoelectric element which vibrates the contact area of the transportunit and the test element is transported along a defined transport pathin the analytical system as soon as the contact area of the transportunit is directly or indirectly contacted with a test element and thecontact area is vibrated by the at least one piezoelectric element. 17.Analytical system for determining an analyte in a sample, the systemcomprising a detection unit for detecting at least one signal that hasbeen changed by an analyte in a sample, an evaluation unit to determineat least one analyte in the sample based on the at least one signal, anda transport unit with a contact area wherein the contact area issuitable for direct or indirect contact with a test element on which thesample can be applied and the transport unit comprises at least onepiezoelectric element which vibrates the contact area of the transportunit and the test element is transported along a defined transport pathin the analytical system as soon as the contact area of the transportunit is directly or indirectly contacted with a test element and thecontact area is vibrated by the at least one piezoelectric element,wherein the transport of the test element is formed to be stopped suchthat the test element is positioned at a predetermined site in theanalytical system.
 18. Method for controlling a transport unit in ananalytical system comprising contacting a test element directly orindirectly by means of a test element carrier with a transport unit ofan analytical system, the transport unit being able to transport thetest element along a transport path in the analytical system,transporting the test element along the transport path, irradiating thetest element or the test element carrier in a first wavelength rangewith a light source which is located along the transport path, anddetecting an optical change which is due to the test element or the testelement carrier wherein the transport unit in the analytical system iscontrolled on the basis of the detected optical change.
 19. Method asclaimed in claim 18, in which the transport unit is controlled by acomparison of the registered detection value with at least onepredefined detection value.
 20. Method as claimed in claim 19, in whichthe test element transport is stopped as soon as a registered detectionvalue falls above or below a predefined value.
 21. Method as claimed inclaim 19, in which at least two detection values are predefined whichare compared with the registered detection values.
 22. Method as claimedin claim 18, in which the test element transport is firstly slowed downbefore a transport stop occurs.
 23. Method as claimed in claim 18, inwhich the light source emits light of less than 600 nm.
 24. Method asclaimed in claim 18, in which the transport of the test elements isinitiated or stopped on the basis of the registered detection value. 25.System for controlling a test element transport comprising a transportunit which is able to transport a test element along a transport pathwithin an analytical system either directly or indirectly by means of atest element carrier, a light source which is located in the analyticalsystem along the transport path such that a test element or test elementcarrier which is transported along the transport path is irradiated in afirst wavelength range and a detector for detecting an optical changewhich is caused by the test element or the test element carrier whereinthe transport unit is contacted with the detector and the transport unitis controlled as a function of the signal detected by the detector. 26.System as claimed in claim 25, in which the transport unit is contactedwith the detector via a control unit.
 27. System as claimed in claim 26,in which the control unit comprises a storage unit in which at least onepredefined detection value is stored and the transport unit iscontrolled by comparing the detected detection value with the presetdetection value.
 28. System as claimed in claim 25, which is suitablefor evaluating a test field of a test element.
 29. System as claimed inclaim 28, in which a test field is optically evaluated using thedetector and/or the light source that are provided for controlling thetransport unit.
 30. System as claimed in claim 25, comprising a testelement which has a test field for an analyte determination and the testfield is detected in order to control the transport unit.
 31. System asclaimed in claim 25, comprising a test element with a mark which isdetected to control the transport unit.
 32. System as claimed in claim31, in which the mark has a reflectance value normalized against whiteof less than 0.2.
 33. System as claimed in claim 31, in which the markis formed by a recess in the test element.